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Failure of Both First and Second
Window of Preconditioning in
Protecting Diabetic Heart
Against Stunning

del Valle, Héctor F.; Lascano, Elena C.;
Negroni, Jorge A.

Department of Physiology, Pharmacology and Biochemistry,
Favaloro University, Buenos Aires, Argentina

Introduction: Ischemic preconditioning (IP) has been shown to protect the heart against infarction, stunning and arrhythmias in a variety of experimental models. Although IP has been studied in human myocardium where it has shown to be cardioprotective, most published works have probed the phenomena occurrence in experimental models with "healthy hearts" and scarce experience exists regarding IP protection in pathologic hearts (ie diabetes). Although early IP (EIP) or second window of protection has been studied in diabetes, contradictory results appeared, and there are no reports on late IP (LIP) or second window of protection.

Objective: Our purpose was to assess whether EIP and LIP protects heart against postischemic myocardial dysfunction in a conscious alloxan-induced diabetic sheep model.

Methods: 20 male sheep were instrumented after 4 weeks of alloxan-induced (1gr total dose) diabetes with a pneumatic cuff occluder positioned at the third terminal portion of the anterior descending coronary artery, a Könisberg pressure transducer and a pair of piezoelectric crystals to study wall thickening behavior during ischemia [I] and reperfusion [R]. Sheep were divide into 3 groups: 1) control (C [n=7], 12 min I followed by 2 hs R); 2) EIP (n=6, six 5 min I - 5 min R periods 45 min before C) and 3) LIP (n=6, the same as EIP but IP periods were performed 24 hs before the sustained 12 min ischemia). Recovery of wall mechanical function was followed during R by measurement of % wall thickening fraction (%WTH) as the integral function of the first, second, third and fourth half hours. All values (Mean±SE) were referred to their basal values considered as 100 %.

Results: Table 1

Conclusion: IP does not protect diabetic heart against stunning in conscious sheep. On the contrary, EIP seems to worsen instead of improving mechanical function.

 

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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
President
Dr. Raúl Bretal
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Dr. Armando Pacher
Technical Committee - CETIFAC
President
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